By: Javier Encinas, PE | December 5, 2018 

ASDIP RETAIN is a structural engineering software for the design of retaining walls. It includes the design of counterfort retaining walls based on the IBC / ACI 318 provisions. This document is a step-by-step design example of a typical counterfort retaining wall using ASDIP RETAIN.

As an example, consider the retaining wall shown below, which supports a flat backfill load. Due to the wall height of 25 feet, the use of counterforts has proven itself to be a more economical solution. The soil bearing capacity is 4 ksf. The backfill density is 115 pcf and the friction angle is 30 degrees. Design the counterfort retaining wall.

counterfort-retaining-wall-design

Design Steps

1.- Enter the geometric dimensions of the wall. In this case, the stem height is 25'-0". Let's try a stem thickness of 12" and a footing thickness of 20". As a rule of thumb, the footing length should be about 0.7 H = 16 ft long, and about 1/4 should be the toe = 4 ft. The At-a-Glance tab shows a summary of the design for a quick overview of your work as you go. The Condensed tab shows a more complete set of results grouped by topic, great for a more detailed overview of your design. The Detailed tab shows a complete set of calculations with exposed formulas and with references to the ACI code.

counterfort-retaining-wall

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counterfort-retaining-wall

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counterfort-retaining-wall

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2.- Enter the loads on the wall. The backfill will be a select material with density = 115 pcf and internal friction angle = 30 deg. We will use the Rankine theory to calculate the lateral soil pressures. The water table is set to zero. No surcharge or concentrated loads were given as part of the problem. The Stability tab shows graphically the pressures and forces on the wall, as well as the stability safety factors per load combination.

counterfort-retaining-wall

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3.- Enter the material properties, which include the allowable soil bearing pressure, the friction coefficient, and the concrete and steel strengths. The Stem tab shows the pressures acting on the stem, and the shear and moment diagrams when the stem is subjected to the lateral pressures, considering the counterforts as the supports.

counterfort-retaining-wall

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4.- Enter the rebars in the stem, counterforts, and footing. ASDIP RETAIN has multiple options to specify the rebars, spacing, and cover.. The Footing tab shows graphically the toe and heel design, including the bearing pressure and design ratios per load combination.

counterfort-retaining-wall

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Takeaway

ASDIP RETAIN includes the design of counterfort retaining walls, with multiple options to optimize the design easily. This example shows that the design can be completed and optimized within minutes.

Detailed information is available about this structural engineering software by visiting ASDIP RETAIN. For engineering background, see the blog post Cantilever Retaining Walls: An Overview of the Design Process (Part 1). You are invited to download the Free 15-day Software Trial, or go ahead and Place your Order.

Best regards,

Javier Encinas, PE

ASDIP Structural Software